1. Field of the Invention
The present invention relates to a preparation process of phthalocyanine derivatives which are useful for dyes, pigments, photoelectric functional materials, recording and memory materials, and compact disk-write once type recording materials in particular. The invention also relates to a halogenated alkoxyphthalocyanine compound and a mixture of the same. Further, the invention relates to an optical recording medium comprising said phthalocyanine compound.
2. Description of the Related Art
Halogenation of phthalocyanine was described in Publication Board Report No. 25,625 and 65,657, and antimony trisulfide or aluminum chloride was used for the catalyst. Consequently, the process could not be applied to phthalocyanines having a readily releasable group such as an alkoxy group. Benzene substituted with an alkoxy group, i.e., ether is decomposed into phenol and alcohol in the presence of aluminum chloride or aluminum bromide. The reaction was reported in the literatures, Chem. Ber., 76B, 900 (1943), J. Org. Chem. 27, 2037 (1962), and Chem. Ber., 93, 2761 (1960). Acids generated as byproducts in halogenation, for example, hydrochloric acid and hydrobromic acid in halogenation by chlorine and bromine, are known as reagents for decomposing the above ether to phenol and alcohol [J. Org. Chem., 6, 852 (1941), Chemical Industries, 1967 , 1138].
Preparation process of halogenated alkoxyphthalocyanine has been disclosed in Japanese Laid-Open Patent 85630 (1975) and J. Chem. Soc., Perkin Trans. I, 1988, 2453-58. In the former process, halogenated phthalocyanine is substituted with alkali metal aliphatic alcoholate or alkali metal phenolate to obtain the desired halogenated alkoxyphthalocyanine or halogenated aryloxyphthalocyanine. In the latter process, the desired halogenated alkoxyphthalocyanine is prepared by by ring closure of dialkoxy-dihalogenophthalonitrile. However, these processes could not be applied to introduce 1 to 4 halogen atoms into tetraalkoxyphthalocyanine.
The inventors have investigated on a recording material suitable for a compact disk-write once type recording medium (hereinafter referred to as CD-WO) and obtained following information.
(1) CD-WO utilizes laser beams in the neighborhood of 780 nm for write and read of record and it is hence important to control absorption coefficient, refractive index and reflectance of the recording material in the neighborhood of 780 nm.
(2) Halogenated alkoxyphthalocyanine is suitable for enhancing sensitivity of CD-WD because decomposition process of phthalocyanine can be controlled by mutual action of the alkoxy groups and the halogen atoms.
The substitution positions of the alkoxy groups are preferably the positions illustrated in the below formulas (9) to (12). A mixture composed of 5 or more isomers or a mixture of compounds having different grade of halogenation is particularly preferred in these halogenated alkoxyphthalocyanines. ##STR2## wherein each R.sup.18 to R.sup.33 is individually a substituted or unsubstituted alkyl group, X is a halogen atom, n indicates numbers of X and is an integer of from 1 to 4, and Met is two hydrogen atoms, a divalent metal atom, or a derivative of trivalent or tetravalent metal. Particularly preferred phthalocyanine is a compound wherein alkoxy groups are secondary, the sum of secondary to quaternary carbon atoms is from 2 to 4, and halogen is bromine.
(3) CD-WO is required to have reflectance of 65% or more. Accordingly, the recording material must have a high refractive index. The inventors have found that refractive index can be improved by introducing an alkoxy group having large steric hindrance into phthalocyanine and further enhanced by additionally introducing a halogen atom, a bromine atom in particular, into the resultant alkoxyphthalocyanine.
(4) In the application of the recording material to a substrate of the recording medium by a solvent casting method such as a spin coating method which is favorable in industry, solubility of the recording material in solvent is an important factor for forming an uniform recording layer.